1. Field of the Invention
This invention relates to a method of and an apparatus for incorporating a torsion spring in a workpiece and more particularly, to a method of and an apparatus for automatically incorporating in a tape cassette a torsion spring which urges a brake member in a reel lock mechanism for preventing a reel from rotating.
2. Description of the Related Art
There has been known a torsion spring incorporating apparatus disclosed in Japanese Unexamined Patent Publication No. 61(1986)-121843. In the torsion spring incorporating apparatus, a guide member in the form of a sleeve is inserted into a coiled portion of a torsion spring, the coiled portion is fitted on a support pin on a workpiece by fitting the guide member on the support pin with the end portion of a first arm of the torsion spring held by a holding means and the torsion spring kept undeflected, the end portion of a second arm is brought into engagement with a first engagement portion of the workpiece, the holding means is rotated with the end portion of the first arm kept held by the holding means, thereby resiliently deflecting the torsion spring, and then the end portion of the first arm is brought into engagement with a second engagement portion of the work.
As the workpiece or device in which the torsion spring is to be incorporated, there has been known a tape cassette such as disclosed in Japanese Unexamined Patent Publication Nos. 1 (1989)-166386 and 3 (1991)-20833. The tape cassette is provided with a lock mechanism which prevents a reel from rotating so that the tape wound around the reel does not slacken when the tape cassette is not in use. The lock mechanism comprises gear teeth formed on the peripheral surface of the reel and a brake member which is adapted to be engaged with the gear teeth and is urged by a torsion spring toward the gear teeth.
However, incorporation of a torsion spring in the manner described above is disadvantageous in that the inner diameter of the coiled portion of the torsion spring must be larger than the outer diameter of the support pin at least by the wall thickness of the guide member and that complicated up and down actions and rotating actions are necessary in incorporation of the torsion spring, which makes it difficult to incorporate torsion springs at a high speed.
That is, the torsion spring comprises an annular coiled portion and a pair of resilient arms projecting from the coiled portion in different directions. When such a torsion spring is incorporated in a workpiece, the coiled portion must be fitted on a support pin and the arms must be in a resiliently deflected state in the incorporated state. Accordingly, the incorporating mechanism should have a function of holding the torsion spring, a function of resiliently deflecting the arms and a function of engaging the deflected arms with engagement portions. Those functions must be accomplished by a compact mechanism which can incorporate the torsion spring at a high speed.
In this point, the conventional torsion spring incorporating apparatus where one arm is first brought into engagement with an engagement portion on a workpiece and then the other arm is resiliently deflected, the incorporating action is complicated and takes a long time, which makes it difficult to increase the working efficiency. Further, since a guide member is first fitted on a support pin and the arms are rotated about the guide member, the inner diameter of the coiled portion of the torsion spring should be larger than the outer diameter of the guide member, which is larger than the outer diameter of the support pin, and accordingly a large incorporating space is required. Further, since the difference between the inner diameter of the coiled portion and the outer diameter of the support pin is large, there is generated a large play between the support pin and the coiled portion and there is a fear that action of the torsion spring on the brake member becomes unstable.